Technical Field
The present invention relates to a hybrid solar-syngas power cycle system comprising a solar reformer, a water evaporator, a plurality of oxygen transport membrane reactors, a plurality of condensers and a gas turbine in which the system is a zero emission fuel cycle and a method for producing syngas using the system in which the combustion products are used as feed gases in order to separate oxygen for combustion and produce syngas in the feed side of the oxygen transport membrane reactor.
Description of the Related Art
The “background” description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description which may not otherwise qualify as prior art at the time of filing, are neither expressly or impliedly admitted as prior art against the present invention.
In the present century, Global warming is the greatest world challenge. Carbon dioxide (CO2) is the main greenhouse gas contributor to global warming (]Nemitallah M. A., Ben-Mansour R., Habib M. A., Numerical investigations of methane fueled oxy-fuel combustion model in a gas turbine combustor: 1. Flow fields, temperature, and species distribution; 2. Effect of CO2 recirculation., Proceedings of the 10th WSEAS conference on heat transfer and environment, Istanbul 2012, ISSN: 2227-4596 and ISBN: 978-1-61804-114-2—incorporated herein by reference in its entirety). Atmospheric CO2 concentration is continuously increasing and causing the average global temperature to rise (IPCC., Contribution of working groups I, II and III to the fourth assessment report of the intergovernmental panel on climate change, Intergovernmental Panel on Climate Change 2007—incorporated herein by reference in its entirety). The largest source of CO2 emissions in the coming decades is the fossil fuel-based power plants (Ghoniem A. F., Needs, resources and climate change: clean and efficient conversion technologies, Progress in Energy Combustion Science 2011, 37:15-51.—incorporated herein by reference in its entirety). This increased rate of CO2 emissions and the global temperature rise forced the development of technologies designed to reduce CO2 emissions resulting from large power plants. Such technologies include carbon capture and storage (CCS), nuclear power and renewable energies such as wind, biomass, and solar in addition to improving the efficiencies of energy conversion (Habib M. A, Nemitallah M. A, Ben-Mansour R., Recent development in oxycombustion technology and its applications to gas turbine combustors and ITM reactors, Energy Fuels 2013, 27, 2-19—incorporated herein by reference in its entirety). The most promising technology which can give a quick response to the global warming due to CO2 emissions (mainly from large power plants) with the lowest available cost is the carbon capture and sequestration technology. There are different available carbon capture technologies which can be applied in the utility industry (Pacala S., Socolow R., Stabilization wedges: solving the climate problem for the next 50 years with current technologies, Science 2004, 305:968-72—incorporated herein by reference in its entirety). Those technologies for carbon capture are post-combustion carbon capture technology, oxy-combustion carbon capture technology and pre-combustion carbon capture technology. Oxy-combustion process is the most promising carbon capture technology. The aim of an oxy-combustion process is to improve the combustion process, reduce the amount of NOx emissions and capture the resultant CO2 at the exit section. Using syngas as a fuel results in a reduction in the CO2 concentration at the exhaust section due to the reduction in the number of carbon atoms in fuel and improved combustion due to the presence of hydrogen. Another solution to reduce the carbon dioxide life cycle is through the use of biomass-derived syngas. This results in increasing the amount of NOx in the exhaust gases. There are three ways where NOx can be formed from the combination of oxygen and nitrogen (Baukal C., Schwartz R., The John Zink combustion handbook, LLC: John Zink Co., 2001; Law C. K., Combustion physics, Cambridge University Press, 2006; Turns S. R., An introduction to combustion concepts and applications, the 2nd edditin, McGraw Hill, 2006; Lieuwen T. C., Yang V., Yetter R., Synthesis gas combustion: fundamentals and applications, Taylor & Francis Group, 2010—each incorporated herein by reference in its entirety). Those three ways include the fuel NOx, thermal NOx and prompt NOx.
In order to reduce the emissions, the oxygen enriched syngas air combustion technique serves as an intermediate solution. The oxygen enriched combustion with air or pure oxygen combustion enhance the fuel combustion process due to the associated reduction of N2 with the oxidizing air. Nitrogen has serious effects on the combustion process as it is an energy carrier medium and it mixes with the combustion gases so that it reduces the concentration of the oxidizing oxygen Cacua K., Amell A., Olmos L., Estudio comparativo entre las propiedades de combustion de la mezcla biogas-aire normaly biogas-aire enriquecido con oxigeno, Ingenieriae et Investigacion 2011, 31, 233-41—incorporated herein by reference in its entirety). In addition, because nitrogen has a high capacity to absorb heat, it absorbs energy and as a result, the combustion efficiency is reduced. In the present disclosure, a combination between both oxy-fuel combustion technology inside ITM reactors and syngas production technology is described. An oxygen transport membrane reactor is used to separate the required oxygen for the syngas-oxygen combustion process in the permeate side of the membrane. In addition, H2 and CO as syngas are separated from H2O and CO2, respectively, in the feed side of the membrane. Integration has been made in this form of a solar transformer for the methane during the day time to the cycle. It is expected by 2020 that the membrane usage in gas separation to be increased by a factor of five (Bernardo P, Drioli E, Golemme G. Membrane gas separation: a review of state of the art. Industrial Chemical Engineering 2009; 48(1):4638-63—incorporated herein by reference in its entirety). Research has been disclosed in order to improve the performance and chemical stability for wide operating range and different operating conditions. ITM reactor technology may be applied for carbon capture by direct combustion of permeated oxygen in the permeate side of the membrane with fuel (Rahimpour M R, Mirvakili A, Paymooni K. A novel water perm-selective membrane dual-type reactor concept for FischereTropsch synthesis of GTL (gas to liquid) technology. ENERGY 2011, 36, 1223-1235—incorporated herein by reference in its entirety). Also, this technology can be used for the production of hydrogen from natural gas (Sjardin M, Damen K J, Faaij A P. Techno-economic prospects of small-scale membrane reactors in a future hydrogen-fuelled transportation sector. ENERGY 2006, 31, 2523-2555—incorporated herein by reference in its entirety). The membrane reactor is a technology for the production of hydrogen from natural gas. It promises economic small-scale hydrogen production, e.g. at refueling stations and has the potential of inexpensive CO2 separation.
The combustion and flame characteristics are also affected while burning syngas with enhanced oxygen air combustion. The syngas combustion with enhanced oxygen improves the flammability limits and the burning velocity. This is because the fuel itself contains hydrogen molecules and also the reaction rates of the fuel in the oxygen-enriched mediums are improved (Burbano H. J., Pareja J., Amell A. A., Laminar burning velocities and flame stability analysis of H2/CO/air mixtures with dilution of N2 and CO2, International Journal of Hydrogen Energy 2011, 36, 3232-42.—incorporated herein by reference in its entirety). Serrano et al. (Serrano C., Herna'ndez J. J., Mandilas C., Sheppard C. G. W., Woolley R., Laminar burning behaviour of biomass gasification-derived producer gas, International Journal of Hydrogen Energy 2008, 33, 851-62—incorporated herein by reference in its entirety) defined the laminar flame speed (burning velocity) to be the propagation speed of the flame for a single dimensional, flat, un-stretched and continuous flame. Laminar flame speed is a very important parameter affecting the combustion characteristics and flame stabilization and behavior. Liu et al. (Liu C., Yan B., Chen G., Bai X. S., Structures and burning velocity of biomass derived gas flames, International Journal of Hydrogen Energy 2010, 35, 542-55—incorporated herein by reference in its entirety) showed that using the laminar flame speed, many premixed flame parameters can be calculated. Those parameters include flash back, extinction, blow off, in addition to the chemical data of gases and turbulent flame propagation. Cuong and Song (Cuong V. H., Song C. K., Combustion and NOx emissions of biomass-derived syngas under various gasification conditions utilizing oxygen-enriched-air and steam, Fuel 2013, 107, 455-464—incorporated herein by reference in its entirety) conducted an experimental study on the combustion of biomass-extracted syngas through a gasification process for different biomass feedstock. Air was used as the oxidizer mixture with different oxygen and steam enrichment concentrations. It was concluded that at higher operating oxygen enrichment levels, the NOx emissions increase may be justified by the increased level of the combustion temperature and high heating value of the biomass-derived syngas. Nemitallah and Habib (Nemitallah M. A., Habib M. A., Experimental and numerical investigations of an atmospheric diffusion oxy-combustion flame in a gas turbine model combustor, Applied Energy, 2013, 11, 401-415—incorporated herein by reference in its entirety) investigated experimentally and numerically a diffusion flame under oxy-fuel combustion and atmospheric pressure conditions inside a small combustor model of a gas turbine. They have studied the oxy-fuel emission and combustion characteristics, in addition to checking the flame stability using methane as a fuel and using oxygen and CO2 as the oxidizer mixture. All of the tested oxy-combustion flames encountered instabilities when the oxygen percent in the oxidizer falls below 25%. For all of the tested flames, flame was blown out for all operating conditions when oxygen percent in the oxidizer is less than 21%.
There are a lot of associated problems with the fossil fuel combustion inside conventional gas turbine and boiler furnaces. The main problem of fossil fuel combustion is the emissions out of the burner, especially CO2, which is the main contributor to the global warming, and NOx, which is the main cause for acid rain. Oxy-combustion can provide a solution to such emission problems of CO2 and NOx. Using oxygen for the combustion process instead of air results in zero NOx emissions because of the lack of nitrogen from the oxidizer. In addition, the combustion products consist mainly of CO2 and H2O. H2O can be separated easily so that CO2 can be captured. The present disclosure not only describes a method for capturing CO2 but also describes full recirculation of exhaust gases inside a loop. The system utilizes an OTR for both oxygen separation and syngas production from the exhaust gases.